Some existing reflex ultrasonic imaging systems make use of a pulse-generating system that has a plane wave generator. A prior art embodiment of a plane wave generator 9 is shown schematically in FIGS. 1A and 1B. FIG. 1A depicts components of the plane wave generator 9. There it is shown a sheet of piezoelectric material 2 positioned between an upper electrode 1 and a lower electrode 3. The plane wave generator 9 produces a longitudinal wave that insonifies an object that is in contact with an imaging platen. By detecting the energy reflected by the object, information about the object may be obtained. The information may be processed by a computer to provide a visual representation of the object via a monitor.
Piezoelectric devices can be used as plane wave generators, and they typically include piezoelectric ceramics, piezoelectric crystals or piezoelectric polymers. To an electronic system that supplies power to the plane wave generator, the plane wave generator looks like a low impedance electrical load. The driving circuits required for such low impedance loads must deliver more power than the driving circuits for high impedance devices.